1. Field of the Invention
This invention relates broadly to surgical instruments. More particularly, this invention relates to an endoscope and endoscopic surgical instruments adapted to be extended into a channel of the endoscope.
2. State of the Art
At the present time there are many instruments made for use in endoscopic medical procedures. Typically, endoscopic instruments are long and flexible cylindrically tubular devices with manually operated handles at their proximal ends and tissue-manipulative cutting, grasping, injecting, or cautery components at their distal ends. Such instruments are introduced into a flexible endoscope which is inserted into the patient through a natural or surgically-created opening. The endoscope includes an elongate portion defining several lumens therethrough and a proximal handle for directing the elongate portion. At least one lumen is provided with an optical imaging system, e.g., a scope, and several lumina or xe2x80x9cworking channelsxe2x80x9d are typically provided for extending endoscopic instruments therethrough. The working channel of the endoscope typically consists of a PTFE-lined cylindrical tube passing from the-proximal (handle) end of the endoscope to its distal (working) end. Working channels are typically 2 to 4 millimeters in inside diameter.
During the medical procedure, the doctor passes one or more endoscopic instruments through the working channels in order to manipulate the tissue being visualized by the optical system of the endoscope. Usually the doctor must repeatedly manipulate the distal end of the instrument by manually pushing and pulling on the proximal portion of the tubular shaft of the endoscopic instrument near where the shaft enters the handle of the endoscope.
The view through an endoscope is highly magnified when seen on the video monitors typically used for these procedures; a field of view that may be a few millimeters across would be enlarged to several inches on the video screen. Accordingly, the instrument must be moved very precisely in very small increments in order to approximate and treat the tissue being visualized. In fact, the doctor must position the distal tip of the endoscopic instrument within a fraction of a millimeter of the desired location in order to achieve desired results. However, because of friction and backlash in the way the instrument passes through the endoscope, achieving this level of accuracy is difficult. For example, an endoscope several feet long may be positioned in the colon of a patient with the distal end of the endoscope tightly reflexed to visualize a particular area of the ascending colon. In such a position, the endoscope is bent into a very sinuous shape in multiple planes. Since the outside diameter of the endoscopic instrument is significantly smaller (e.g., 2.2 mm) than the inside diameter of the working channel (e.g., 3.2 mm), a large clearance space exists between the instrument and the channel. When the instrument is pulled back, the tension on the instrument causes the instrument to be pulled taut and the instrument naturally assumes the shortest path through the channel. When the instrument is pushed forward, friction causes it to assume the longest path through the channel (that is, the shaft of the instrument must xe2x80x9cfillxe2x80x9d the working channel before the distal end of the: instrument begins to move). As a result, quite a bit of backlash (lost motion) is experienced by the doctor when the doctor tries to manipulate the distal end of the instrument. If it is necessary to pull the tip back a bit, the backlash must first be pulled out before the distal end can be retracted. If the doctor pulls the instrument back a little too far, the doctor must then push it several millimeters forward before there is any motion at all at the distal end. During this manipulation, the endoscopic instrument alternately assumes the longest-path and shortest-path positions within the working channel of the endoscope. If this backlash can be reduced or eliminated, the manipulation of the distal end of the endoscopic instrument can be made much easier and more positive, and the doctor can achieve his desired positioning more rapidly. However, this is not a simple problem to overcome for several reasons.
While the backlash situation described above can be reduced or substantially eliminated if the clearance between the outside of the endoscopic instrument and the inside of the working channel of the endoscope can be reduced, this is not a practical solution. It is often necessary to inject fluid (or to operate suction) through the annular space between these two structures. If the instrument shaft were to substantially fill up the space within the working channel, the backlash would be reduced, but there would be greatly reduced ability to conduct fluid through the working channel around the instrument. In fact, because of the nature of fluid flow, as the aspect ratio of the annular clearance space (the ratio of the thickness of the fluid channel to its circumferential length) becomes small, the impedance to fluid flow grows disproportionately to the reduction in cross-sectional area of the fluid passage.
In addition, as the diameter of the shaft approaches the inside diameter of the working channel, the area of contact between the instrument and the working channel becomes larger, particularly since the working channel is usually made of a relatively soft material, PTFE. This increase in contact area between these parts results in an increase in frictional drag on the instrument when the doctor attempts to move it through the channel.
It is therefore an object of the invention to provide an endoscopic system with little or no backlash between the endoscope and the endoscopic instrument.
It is also an object of the invention to provide an endoscopic system which reduces the backlash between an endoscopic instrument an a working channel of an endoscope, while maintaining open area therebetween for permitting fluid flow.
In accord with these objects, which will be discussed in detail below, an endoscopic system is provided where either a portion of the endoscopic instrument or a portion of the working channel is provided with a non-circular cross-section.
Generally, an endoscopic instrument includes an elongate flexible tubular member having proximal and distal ends, a control member having proximal and distal ends and extending through the tubular member, an end effector assembly coupled to the distal ends of the tubular member and the control member, and a handle means for moving the control member relative to the tubular member to operate the end effector assembly. According to a first embodiment of the invention, the distal end of the elongate flexible tubular member of the endoscopic instrument has an outer surface having a non-circular cross-sectional shape. The non-circular cross-sectional shape may be provided to the portion of the tubular member by radially spacing a plurality of fins or other projections about the peripheral (exterior) of the portion, or by providing the portion with a polygonal cross-sectional shape. Where fins are provided, the fins can be quite small and will only have a minimal effect on the fluid-flow cross-sectional area between the working channel and the endoscopic instrument. Thus, the resulting endoscopic instrument will have significantly reduced backlash while maintaining adequate fluid flow in the working channel. In addition, the fins or corners of the polygonal shape provide few and relatively small contact points so that the endoscopic instrument may be readily advanced through the lumen (working channel) of an endoscope.
According to a second embodiment of the invention, an endoscope is provided having a proximal handle, and elongate flexible distal portion having an imaging channel provided with an imaging system and a working channel having an interior surface and adapted to receive an endoscopic instrument therethrough. The working channel along its length has a preferably substantial portion at which the working channel has a non-circular cross-sectional-shape. The non-circular cross-sectional shape can be provided to the working channel by providing the interior surface of the working channel with a plurality of radially spaced and inwardly directed ribs or other projections or by providing the interior surface of the working channel with a polygonal shape. The ribs can be quite small and will only have a minimal-effect on the fluid flow cross sectional area between the working channel and the endoscopic instrument. Therefore, the resulting endoscope will reduce the backlash of an endoscopic instrument inserted therein while maintaining adequate fluid flow in the working channel. Additionally, the endoscopic instrument can be readily advanced through the working channel, as there will be few and relatively small contact points between the two.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.